1. Field of the Invention
The invention relates to a polyurea grease composition comprising a lubricating oil and a thickener. The thickener is the reaction product of a diisocyanate with a monoamine, a diamine and a selected copolymer. The copolymer is either a polyoxyalkylene glycol or a polyoxyalkylene diamine.
2. Description of Other Related Methods in the Field
Polyurea grease compositions are used commercially to provide lubrication at high temperature for extended periods of time. The polyurea thickening agents are formed by reacting an isocyanate with an amine mixture in a base oil to yield the polyurea grease composition.
U.S. Pat. No. 4,661,276 to J. E. Stemke discloses a polyurea thickened grease in which the amine component is selected from the group consisting of polyesters, polyamides, polyurethanes, polyamines or polyoxides.
U.S. Pat. No. 3,801,506 to E. A. Cross et al discloses greases thickened with lithium soaps or mixtures of lithium soaps and calcium soaps. One additive to the grease composition is a copolymer of polyoxyethylene glycol and polyoxypropylene glycol. The copolymers comprise 75 to 90 parts by weight of propoxy groups and 25 to 10 parts by weight ethoxy groups. Molecular weights range from 300 to 15,000. The finished grease comprises 0.1 wt % to 5 wt % of the copolymer.